Page 11 - Math Smart - 7

Spotlight
To discover the first 25 prime numbers, sift out all the composite numbers
between 1 and 100 using multiples. Currently, the largest
Refer to the hundred grid below. known prime number
was found in 2018 and is
O Cross out the number 1 since it is not prime.
23 249 425 digits long. It
© Circle the 2 and then cross out all the multiples of 2.
was found by the Great
© Circle the 3 and then cross out all the multiples of 3. Internet Mersenne Prime
Search (GIMPS).
O Do the same for 5 and 7 and their multiples.
© Circle the remaining numbers. These are the first 25 prime numbers. Find out more.

© List the 25 prime numbers less than 100 in ascending order.

@ 3 X 5 6 7 8 9 10
n 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30

31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50

51 52 53 54 55 56 57 58 59 60

61 62 63 64 65 66 67 68 69 70
71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90

91 92 93 94 95 96 97 98 99 100

Multiples

Multiples of a number are the results of multiplying the number by a positive
whole number.

15 is a multiple of 3 3 Is a factor of 15

\ /
15 = 3X5
15 is also a multiple of 5 ^ ^ 5 is a factor of 15

308 = 4 X 7 X 11
/ \

308 is a multiple of 4, 7 and 11 4, 7 and 11 are all factors of 308